/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * kernel/task/task_spawn.c
 *
 *   Copyright (C) 2013 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#include <sys/wait.h>
#include <sched.h>
#include <spawn.h>
#include <debug.h>

#include "sched/sched.h"
#include "group/group.h"
#include "task/spawn.h"
#include "task/task.h"

#ifndef CONFIG_BUILD_KERNEL

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/****************************************************************************
 * Private Types
 ****************************************************************************/

/****************************************************************************
 * Public Data
 ****************************************************************************/

/****************************************************************************
 * Private Data
 ****************************************************************************/

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: task_spawn_exec
 *
 * Description:
 *   Execute the task from the file system.
 *
 * Input Parameters:
 *
 *   pidp - Upon successful completion, this will return the task ID of the
 *     child task in the variable pointed to by a non-NULL 'pid' argument.|
 *
 *   path - The 'path' argument identifies the file to execute.  If
 *     CONFIG_BINFMT_EXEPATH is defined, this may be either a relative or
 *     or an absolute path.  Otherwise, it must be an absolute path.
 *
 *   attr - If the value of the 'attr' parameter is NULL, the all default
 *     values for the POSIX spawn attributes will be used.  Otherwise, the
 *     attributes will be set according to the spawn flags.  The
 *     following spawn flags are supported:
 *
 *     - POSIX_SPAWN_SETSCHEDPARAM: Set new tasks priority to the sched_param
 *       value.
 *     - POSIX_SPAWN_SETSCHEDULER: Set the new tasks scheduler priority to
 *       the sched_policy value.
 *
 *     NOTE: POSIX_SPAWN_SETSIGMASK is handled in ps_proxy().
 *
 *   argv - argv[] is the argument list for the new task.  argv[] is an
 *     array of pointers to null-terminated strings. The list is terminated
 *     with a null pointer.
 *
 * Returned Value:
 *   This function will return zero on success. Otherwise, an error number
 *   will be returned as the function return value to indicate the error.
 *   This errno value may be that set by execv(), sched_setpolicy(), or
 *   sched_setparam().
 *
 ****************************************************************************/

static int task_spawn_exec(FAR pid_t *pidp, FAR const char *name, main_t entry, FAR const posix_spawnattr_t *attr, FAR char *const *argv)
{
	size_t stacksize;
	int priority;
	int pid;
	int ret = OK;

	/* Disable pre-emption so that we can modify the task parameters after
	 * we start the new task; the new task will not actually begin execution
	 * until we re-enable pre-emption.
	 */

	sched_lock();

	/* Use the default task priority and stack size if no attributes are provided */

	if (attr) {
		priority = attr->priority;
		stacksize = attr->stacksize;
	} else {
		struct sched_param param;

		/* Set the default priority to the same priority as this task */

		ret = sched_getparam(0, &param);
		if (ret < 0) {
			goto errout;
		}

		priority = param.sched_priority;
		stacksize = CONFIG_TASK_SPAWN_DEFAULT_STACKSIZE;
	}

	/* Start the task */

	pid = task_create(name, priority, stacksize, entry, argv);
	if (pid < 0) {
		ret = get_errno();
		sdbg("ERROR: task_create failed: %d\n", ret);
		goto errout;
	}

	/* Return the task ID to the caller */

	if (pid) {
		*pidp = pid;
	}

	/* Now set the attributes.  Note that we ignore all of the return values
	 * here because we have already successfully started the task.  If we
	 * return an error value, then we would also have to stop the task.
	 */

	if (attr) {
		(void)spawn_execattrs(pid, attr);
	}

	/* Re-enable pre-emption and return */

errout:
	sched_unlock();
	return ret;
}

/****************************************************************************
 * Name: task_spawn_proxy
 *
 * Description:
 *   Perform file_actions, then execute the task from the file system.
 *
 *   Do we really need a proxy task in this case?  Isn't that wasteful?
 *
 *   Q: Why can we do what we need to do here and the just call the
 *      new task's entry point.
 *   A: This would require setting up the name, priority, and stacksize from
 *      the task_spawn, but it do-able.  The only issue I can think of is
 *      that TinyAra supports task_restart(), and you would never be able to
 *      restart a task from this point.
 *
 *   Q: Why not use a starthook so that there is callout from task_start()
 *      to perform these operations?
 *   A: Good idea, except that existing task_starthook() implementation
 *      cannot be used here unless we get rid of task_create and, instead,
 *      use task_init() and task_activate().  start_taskhook() could then
 *      be called between task_init() and task)activate().  task_restart()
 *      would still be an issue.
 *
 * Input Parameters:
 *   Standard task start-up parameters
 *
 * Returned Value:
 *   Standard task return value.
 *
 ****************************************************************************/

static int task_spawn_proxy(int argc, FAR char *argv[])
{
	int ret;

	/* Perform file actions and/or set a custom signal mask.  We get here only
	 * if the file_actions parameter to task_spawn[p] was non-NULL and/or the
	 * option to change the signal mask was selected.
	 */

#ifndef CONFIG_DISABLE_SIGNALS
	DEBUGASSERT(g_spawn_parms.file_actions || (g_spawn_parms.attr && (g_spawn_parms.attr->flags & POSIX_SPAWN_SETSIGMASK) != 0));
#else
	DEBUGASSERT(g_spawn_parms.file_actions);
#endif

	/* Set the attributes and perform the file actions as appropriate */

	ret = spawn_proxyattrs(g_spawn_parms.attr, g_spawn_parms.file_actions);
	if (ret == OK) {
		/* Start the task */

		ret = task_spawn_exec(g_spawn_parms.pid, g_spawn_parms.u.task.name, g_spawn_parms.u.task.entry, g_spawn_parms.attr, g_spawn_parms.argv);

#ifdef CONFIG_SCHED_HAVE_PARENT
		if (ret == OK) {
			/* Change of the parent of the task we just spawned to our parent.
			 * What should we do in the event of a failure?
			 */

			int tmp = task_reparent(0, *g_spawn_parms.pid);
			if (tmp < 0) {
				sdbg("ERROR: task_reparent() failed: %d\n", tmp);
			}
		}
#endif
	}

	/* Post the semaphore to inform the parent task that we have completed
	 * what we need to do.
	 */

	g_spawn_parms.result = ret;
#ifndef CONFIG_SCHED_WAITPID
	spawn_semgive(&g_spawn_execsem);
#endif
	return OK;
}

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: task_spawn
 *
 * Description:
 *   The task_spawn() function will create a new, child task, where the
 *   entry point to the task is an address in memory.
 *
 * Input Parameters:
 *
 *   pid - Upon successful completion, task_spawn() will return the task ID
 *     of the child task to the parent task, in the variable pointed to by
 *     a non-NULL 'pid' argument.  If the 'pid' argument is a null pointer,
 *     the process ID of the child is not returned to the caller.
 *
 *   name - The name to assign to the child task.
 *
 *   entry - The child task's entry point (an address in memory)
 *
 *   file_actions - If 'file_actions' is a null pointer, then file
 *     descriptors open in the calling process will remain open in the
 *     child process (unless CONFIG_FDCLONE_STDIO is defined). If
 *     'file_actions' is not NULL, then the file descriptors open in the
 *     child process will be those open in the calling process as modified
 *     by the spawn file actions object pointed to by file_actions.
 *
 *   attr - If the value of the 'attr' parameter is NULL, the all default
 *     values for the POSIX spawn attributes will be used.  Otherwise, the
 *     attributes will be set according to the spawn flags.  The
 *     task_spawnattr_t spawn attributes object type is defined in spawn.h.
 *     It will contains these attributes, not all of which are supported by
 *     TinyAra:
 *
 *     - POSIX_SPAWN_SETPGROUP:  Setting of the new task's process group is
 *       not supported.  TinyAra does not support process groups.
 *     - POSIX_SPAWN_SETSCHEDPARAM: Set new tasks priority to the sched_param
 *       value.
 *     - POSIX_SPAWN_SETSCHEDULER: Set the new task's scheduler policy to
 *       the sched_policy value.
 *     - POSIX_SPAWN_RESETIDS: Resetting of the effective user ID of the child
 *       process is not supported.  TinyAra does not support effective user
 *       IDs.
 *     - POSIX_SPAWN_SETSIGMASK: Set the new task's signal mask.
 *     - POSIX_SPAWN_SETSIGDEF:  Resetting signal default actions is not
 *       supported.  TinyAra does not support default signal actions.
 *
 *     And the non-standard:
 *
 *     - TASK_SPAWN_SETSTACKSIZE:  Set the stack size for the new task.
 *
 *   argv - argv[] is the argument list for the new task.  argv[] is an
 *     array of pointers to null-terminated strings. The list is terminated
 *     with a null pointer.
 *
 *   envp - The envp[] argument is not used by TinyAra and may be NULL.
 *
 * Returned Value:
 *   task_spawn() will return zero on success. Otherwise, an error number
 *   will be returned as the function return value to indicate the error:
 *
 *   - EINVAL: The value specified by 'file_actions' or 'attr' is invalid.
 *   - Any errors that might have been return if vfork() and excec[l|v]()
 *     had been called.
 *
 ****************************************************************************/

int task_spawn(FAR pid_t *pid, FAR const char *name, main_t entry, FAR const posix_spawn_file_actions_t *file_actions, FAR const posix_spawnattr_t *attr, FAR char *const argv[], FAR char *const envp[])
{
	struct sched_param param;
	pid_t proxy;
#ifdef CONFIG_SCHED_WAITPID
	int status;
#endif
	int ret;

	svdbg("pid=%p name=%s entry=%p file_actions=%p attr=%p argv=%p\n", pid, name, entry, file_actions, attr, argv);

	/* If there are no file actions to be performed and there is no change to
	 * the signal mask, then start the new child task directly from the parent task.
	 */

#ifndef CONFIG_DISABLE_SIGNALS
	if ((file_actions == NULL || *file_actions == NULL) && (attr == NULL || (attr->flags & POSIX_SPAWN_SETSIGMASK) == 0))
#else
	if (file_actions == NULL || *file_actions == NULL)
#endif
	{
		return task_spawn_exec(pid, name, entry, attr, argv);
	}

	/* Otherwise, we will have to go through an intermediary/proxy task in order
	 * to perform the I/O redirection.  This would be a natural place to fork().
	 * However, true fork() behavior requires an MMU and most implementations
	 * of vfork() are not capable of these operations.
	 *
	 * Even without fork(), we can still do the job, but parameter passing is
	 * messier.  Unfortunately, there is no (clean) way to pass binary values
	 * as a task parameter, so we will use a semaphore-protected global
	 * structure.
	 */

	/* Get exclusive access to the global parameter structure */

	spawn_semtake(&g_spawn_parmsem);

	/* Populate the parameter structure */

	g_spawn_parms.result = ENOSYS;
	g_spawn_parms.pid = pid;
	g_spawn_parms.file_actions = file_actions ? *file_actions : NULL;
	g_spawn_parms.attr = attr;
	g_spawn_parms.argv = argv;
	g_spawn_parms.u.task.name = name;
	g_spawn_parms.u.task.entry = entry;

	/* Get the priority of this (parent) task */

	ret = sched_getparam(0, &param);
	if (ret < 0) {
		int errcode = get_errno();

		sdbg("ERROR: sched_getparam failed: %d\n", errcode);
		spawn_semgive(&g_spawn_parmsem);
		return errcode;
	}

	/* Disable pre-emption so that the proxy does not run until waitpid
	 * is called.  This is probably unnecessary since the task_spawn_proxy has
	 * the same priority as this thread; it should be schedule behind this
	 * task in the ready-to-run list.
	 */

#ifdef CONFIG_SCHED_WAITPID
	sched_lock();
#endif

	/* Start the intermediary/proxy task at the same priority as the parent
	 * task.
	 */

	proxy = task_create("task_spawn_proxy", param.sched_priority, CONFIG_POSIX_SPAWN_PROXY_STACKSIZE, (main_t)task_spawn_proxy, (FAR char *const *)NULL);
	if (proxy < 0) {
		ret = get_errno();
		sdbg("ERROR: Failed to start task_spawn_proxy: %d\n", ret);

		goto errout_with_lock;
	}

	/* Wait for the proxy to complete its job */

#ifdef CONFIG_SCHED_WAITPID
	ret = waitpid(proxy, &status, 0);
	if (ret < 0) {
		sdbg("ERROR: waitpid() failed: %d\n", errno);
		goto errout_with_lock;
	}
#else
	spawn_semtake(&g_spawn_execsem);
#endif

	/* Get the result and relinquish our access to the parameter structure */

	ret = g_spawn_parms.result;

errout_with_lock:
#ifdef CONFIG_SCHED_WAITPID
	sched_unlock();
#endif
	spawn_semgive(&g_spawn_parmsem);
	return ret;
}

#endif							/* CONFIG_BUILD_KERNEL */
